Islamic and human rights groups in Asia expressed outrage at the grisly death of 78 detained Muslim protesters in southern Thailand and warned of more violence unless justice is done.

Neighbouring countries urged Bangkok to prevent an escalation of the crisis, which erupted halfway into the holy fasting month of Ramadan and was likened by a Malaysian Islamic party to a "holocaust" for Thailand's Muslim minority.

Thai Prime Minister Thaksin Shinawatra vowed an official investigation after initially blaming the effects of fasting and drug use for the high death toll.

Most of the detainees suffocated while packed inside trucks transporting them to an army camp in Pattani province after being arrested in the wake of clashes on Monday with security forces.

Buddhist-dominated Thailand belongs to the Association of Southeast Asian Nations (Asean), where Muslims constitute about half the estimated 500 million people and Islamic extremists are exploiting grievances to recruit followers.

Former Asean secretary-general Rodolfo Severino warned that unless the incident was properly investigated, Muslim minorities in Southeast Asia "will feel even more vulnerable and besieged" and "that's a formula for trouble".

"We also must remember that more than any other group of religious adherents, the Muslims identity with fellow Muslims more closely because of this concept of the Muslim community, whatever nationality they are," he said.

A spokesman for the Singapore foreign ministry said "we regret the tragic loss of so many lives" and "trust that the Thai government will take steps to return the situation to normalcy as soon as possible".

Pak Lah expresses concern

In Muslim-majority Malaysia, which borders the troubled Thai provinces, Prime Minister Abdullah Ahmad Badawi said he phoned Thaksin to express concern and tell him that Malaysia was watching very closely what is happening.

"I have also expressed my feelings that in the month of Ramadan, incidents of this nature can bring a lot of unhappiness and create anger and animosity among members of the community," he said.

An official of Malaysia's opposition Islamic party PAS described the detainees' deaths as "a holocaust of the modern era" and said that if the Thai military does not exercise restraint, violence could spill over the border since many Malaysians have relatives on the Thai side.

In Indonesia, the world's largest Muslim-populated nation, foreign ministry spokesman Marty Natalegawa said Jakarta was concerned by the escalating tension in southern Thailand "but we are confident that the government of Thailand will conduct an appropriate inquiry".

Muhammadiyah, Indonesia's second-largest Muslim social organisation, issued a statement which "strongly condemns the dehumanising action carried out by the Thai security forces toward Muslims in southern Thailand and demands that the tragedy be referred to as a crime against humanity."

The independent Malaysian Human Rights Commission said that if the Thai government did not end the violence in the south, it could be viewed as ethnic cleansing by some people and exploited by extremist groups.

Outside Asia, the US government called for a thorough inquiry. Iran condemned the deaths and urged the authorities to prosecute those responsible.

'Brutal massacre'

Thaksin first blamed Ramadan fasting and drug use among protesters for the high death toll, but said yesterday that "we feel sorry" and that the detaines should not have died in custody.

The Hong Kong-based Asian Human Rights Commission said "the latest mass killing" was the result of a weakening of controls over the police and armed forces in the restive region, and said Bangkok "has blatantly ignored the signs of impending disaster".

Largely Muslim Pakistan's opposition six-party Islamist alliance slammed the deaths as a "brutal massacre" and called on the United Nations to investigate.

"The killings in Thailand were the outcome of a fear of terror the United States has created all over the world," said Liaquat Baloch, secretary general of the Muttahida Majlis-e-Amal alliance.

"Law enforcing agencies are unnerved everywhere and they overreact even in ordinary crime cases."